Deflection yoke having coil locating projections

ABSTRACT

Deflection coil unit having at least one pair of saddle-type coils surrounded by the flaring inner surface of a ferromagnetic yoke ring provided with ridge-shaped internal projections ground to fit the flaring outer surface of the pair of saddle coils.

United States Patent Meier 1451 Mar. 28, 1972 [54] DEF LECTION YOKE HAVING COIL [56] References Cited LOCATING PROJECTIONS UNITED STATES PATENTS [72] g 'ggtzf jgfgl'i xz Emmasmgel 3,310,763 3/1967 Thompson .335/213 3,246,192 4/1966 Torsch [73] Assignee: U.S. Philips Corporation, New York, NY. 2,901,650 8/1959 Barkow et a1. ..335/213 X [22] Filed: lune 1970 Primary Examiner-George Harris [211 Ap NO; 45,325 Attorney-Frank R. Trifari [57] ABSTRACT [30] Foreign Application Priority Data Deflection coil unit having at least one pan of saddle-type June 19, 1969 Netherlands ..6909344 coils surrounded by the fl i inner surface f a ferromag netic yoke ring provided with ridge-shaped internal projec- [52] U.S. Cl ..335/2l0, 335/213 tions ground to fi the fl i outer surface f the pair f [51] Int. Cl ..H0lf 7/00 dle coils [58] Field ofSearch ..335/2l0,298,213;313/75 3 Claims, 2 Drawing Figures DEFLECTION YOKE HAVING COIL LOCATING PROJECTIONS This invention relates to a deflection coil set comprising at least one pair of saddle coils surrounded by a magnetically closed ferrite yoke ring whose inner surface joins the outer surface of the pair of saddle coils.

The yoke ring consists of two joined halves preferably obtained by dividing the sintered yoke, which is in the form of a single ring, into two portions. It is known that during the sintering operation the ring is considerably deformed so that it is not possible to cause the shape of the ring to match accurately that of the saddle coils, which can themselves be wound in a comparatively accurate and reproducible manner. Therefore, it is the customary practice to make the yoke rings oversize by about percent and then to fill out interstice wholly or partly with insulating material, for example, a foam plastic. Accurate positioning of the yoke as required, for example, in wide angle color television display tubes having an angle of deflection of l l0 cannot be ensured in this way or at least cannot be obtained at low cost.

According to the invention a cheap solution is obtained by providing the flaring inner surface of the yoke ring with at least three projections ground to an extent such that the ring with the ground surfaces bears on the outer surface of the pair of saddle coils so that the position of the ring relative to the pair of coils is determined in an axial direction by said ground surfaces. The grinding operation is by nature very accurate and because only a few small elevated parts have to be ground the cost is low.

it should be noted that deflection coil sets comprising yoke rings with internal ridges are known (so called castellated rings). In this case the coils are located in the spaces between the ridges. The latter are not intended to position the ring relative to the outer surface of a set of coils and are therefore not ground. The invention will best be understood from the following detailed description taken in conjunction with the accompanying drawing in which FIG. 1 shows a known device in a partial axial sectional view, and

FIG. 2 provides a the invention.

FIG. 1 shows a deflection coil set comprising a pair of saddle coils l for frame deflection one of the pair being shown. The pair of line deflection coils arranged inside the frame deflection coils is omitted for the sake of clarity. The pair of coils 1 is surrounded by a yoke ring 3 (in solid lines) composed of ferrite material. The yoke ring has a flaring inner surface which matches as far as possible the similarly shaped outer surface of the pair of coils 1. From the Figure it will be apparent that a yoke ring 3 (in dashed lines) having shrunk perspective view of one embodiment of only slightly more than the ring 3 during the sintering operation will occupy a position considerably shifted in an axial direction.

This disadvantage does not occur when a (bepartite) yoke ring as shown in FIG. 2 is used. The inner side of this ring is provided with at least three projections, in this case four approximately axial ridges 5 (two of them are shown in FIG. 2), which are ground so that the four ground surfaces 7 are located in a plane matching the outer surface of the pair of coils 1. This may be achieved readily by means of a grinding drum whose grinding surface has said shape. A jig of approximately the same shape may be used in a known manner for fixing (clamping) the yoke ring in the grinding machine. It is then ensured that all rings to be ground are set in the same axial position in the grinding machine. By these steps it is ensured that in assembling the set of coils the ground surfaces 7 of the yoke ring will bear on the outer surface of the associated pair of coils l in the correct axial position.

Since the ridges 5 to be ground have only a small surface, the costs of grinding are low. If desired, instead of using ridges two or more axially sequential projections may be used instead of one ridge. While the ridges 5 are ground, a number of radial elevations 9 provided on the largest outer periphery of the ring 3 may be ground for holding a plastics ring (not shown) for axially guiding the whole set of coils inside an insulating cage.

Such cages, for accommodating an axially displaceable set of deflection coils, are frequently used in color television. The yoke ring 3 may, if desired, hold two toroidally wound frame deflection coils which are arranged individually between two adjacent projections 5. The saddle coils joined by the ground surfaces 7 then serve as line deflection coils.

We claim:

1. A deflection yoke assembly comprising at least one pair of saddle coils surrounded by magnetically closed ferrite yoke ring having a flaring inner surface that approximately matches the outer surface of the pair of saddle coils, said flaring inner surface of the yoke ring being provided with at least three projections with ground surfaces located in a plane that matches the outer surface of the pair of saddle coils and bearing on the outer surface of the pair of saddle coils so as to determine the position of the ring relative to the pair of coils in an axial direction.

2. A deflection yoke assembly as claimed in Claim 1 characterized in that the projections are shaped in the form of ridges extending approximately in an axial direction from the inner surface of the ring.

3. A deflection yoke assembly as claimed in claim 2 wherein said yoke ring comprises a sintered ferrite sleeve having a cylindrical portion and an outwardly flaring portion. 

1. A deflection yoke assembly comprising at least one pair of saddle coils surrounded by magnetically closed ferrite yoke ring having a flaring inner surface that approximately matches the outer surface of the pair of saddle coils, said flaring inner surface of the yoke ring being provided with at least three projections with ground surfaces located in a plane that matches the outer surface of the pair of saddle coils and bearing on the outer surface of the pair of saddle coils so as to determine the position of the ring relative to the pair of coils in an axial direction.
 2. A deflection yoke assembly as claimed in Claim 1 characterized in that the projections are shaped in the form of ridges extending approximately in an axial direction from the inner surface of the ring.
 3. A deflection yoke assembly as claimed in claim 2 wherein said yoke ring comprises a sintered ferrite sleeve having a cylindrical portion and an outwardly flaring portion. 